It's official: The El Reg "Paper Aircraft Released Into Space" (PARIS) vehicle has been christened Vulture 1 by popular vote, and with this formality out of the way we can move on to pondering just how our audacious upper atmosphere programme is actually going to work.
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How about...

"Something else which you lot might want to ponder is just how we can release the Vulture 1 from the helium balloon at a predetermined altitude, without having to put together a mechanism which will add greatly to the payload weight. Any thoughts?"

A simple latex balloon would do the trick- the difference between the air pressure internal/external would make the balloon pop at a particular altitude (some testing needed to determine the amount of air to prefill the balloon with). You could then connect the PARIS directly to the balloon (though this runs the risk of non-separation due to the balloon not disintergrating fully) or have some form of holding mechanism which holds the PARIS as long as the balloon is inflated.

Been there, done that

@ Andrew Moore

'A simple latex balloon would do the trick'

And it seems somehow appropriate to use latex around PARIS.

This project makes me proud(ish) to be British once more - what with Top Gear firing a Robin Reliant into the stratosphere and the Reg building a high altitude paper plane it's like the heady days of the Blue Streak and Bryllcreem.

May I suggest

@How about

@ Andrew Moore / balloons

I was about to suggest balloons too. What I'm picturing is a sloping launch ramp so that the PARIS is always in a pointing-downwards position. The only thing stopping it from sliding off and launching is the balloon. When the balloon bursts, the plane slides free, problem solved. The only possible danger is entanglement on balloon fragments, but I'm picturing the balloon restrained from underneath the lip of the bottom of the ramp, so it will fall underneath while the PARIS slides past. Plausible?

I hope you realise..

Release Mechanism

How about a "fuse", a glass vial filled with a gas that breaks, a la the latex suggestion above, at a specified range in altitude? You could make the fasteners from a durable plastic. This would solve the "incomplete separation" issue while keeping the payload light enough for PARIS to get off on it.. With it. Take off with it.

Release

First thing that came to mind would be a glass stick containing a pressurised gas with a certain thickness of glass. The stick would be tied onto the balloon and the plane. When the pressure outside the stick becomes too little, it will rupture, splitting the connection between the plane and the balloon and drop the plane.

How to pop a balloon at a predictable height

This is pretty easy. You have a GPS tracker already, so just use a nylon tether between the aircraft and the balloon and have the GPS controller connect the battery to a bit of nichrome wire wrapped around the tether. When the GPS shows that the aircraft is falling, turn off the current. Shouldn't weigh more than a few grammes.

Separation anxiety

The higher you go the cooler it gets...

And this will affect the electronics modules. Most electronic devices like that nice stable region of 0 to +40 deg C for operation. At 10,000m the temperature is typically -55deg C (if the Moving Map on the 767 is to be believed). So the GPS might want a bit of a woolly jumper and hat.

Simple or complicated?

Simple - how high would the balloon go anyway? if the balloon won't go above a certain height anyway then it won't matter when it releases, just set a timer (digital watch circuit or an incrementing ASIC) to ignite a small charge (you only need to blow the PARIS off!) to affect the release.

Complicated - well, talk to NASA, but assuming you want a certain altitude you could use the (A)GPS for this as well since that would give you an altitude reading as well as the earth-bound position.

Ok - a silly one: a REALLY long bit of string, or another ballon carrying a small person with a pair of scissors on a stick.

How about a really long bit of string?

If you tie a bit of string to the release mechanism, then hold on to the other end and let the balloon go, then so long as you've cut the bit of string to the correct length then when the balloon gets high enough the string will pull on the release mechanism and launch your Vulture 1.

As an added bonus, if you then tied the ground control end of the string to a fence or lamp post, you could leave the balloon up there as a sort of 'space elevator lite'.

Balloon and self-guiding glider

Take a gander at this web site:

http://members.shaw.ca/sonde/index.htm

This plane flew several times before it was lost when it hit the top of a mountain. It used a weather balloon for launch though it was a simple balsa and tissue model rather than paper. It took photos all the way down from 70,000 ft while guiding itself back to its launch point.

As it was a one man project, something like it should be easily done by a gang of El Reg hacks. Just make sure you have a competent model aircraft builder in the team. This way you're more likely to get a plane that flies rather than plummets.

As JetSetJim says, talk to the guys at CUspace since they have several successful weather balloon flights under their belts.

Release Mechanism !

@Andrew Moore

<<A simple latex balloon would do the trick- the difference between the air pressure internal/external would make the balloon pop at a particular altitude (some testing needed to determine the amount of air to prefill the balloon with)>>

Well good idea. 'Course, if it's called PARIS, then the obvious source of the release balloon might be procured from the local barber. "Something for the weekend, Sir?*"

Perfect for El Reg.

(Actually, clockwork 'dethermalisers' are cheap-ish and available. Or, just fly the fuc*ker over London, and let the RAF do the job for you...)

* Once, I heard a story about BBC wanting to waterproof microphones. One BBC engineer went to the chemist, and bought a few different brands of condoms, opened them up IN STORE! - and measured the thickness with a micrometer.

Chemist wandered over and said, "Bit choosy, are we, Sir?". Probably not true, but an amusing read.

Altitude release

Presumably the rate of climb of the baloon is constant predictable, allowing some sort of timed release mechanism could be used (in the vein of the time pencils used to detonate explosives during WW2).

Thoughts on vehicle electronics

Ok some of this isnt entirely applicable to the vulture1, especially as the airframe id choose for such a plane would be a cheap EPS foam model plane, however if you want some data logging, photo taking and possibly a return to home feature so you dont have to go looking for it after release you should really have a look at the open source paparazzi UAV project.

http://paparazzi.enac.fr/wiki/Main_Page

Basically all you need to build a GPS guided remote/autonomous UAV at very low cost. Whilst the radio link they use for telemetry wont work over the distance you are planning its a modular design and im sure a better link could be substituted if you wanted real time control, it would probably also be possible to have it set up to make its run autonomously and glide back to home base allowing you to retrieve the photos/video without the hassle of going looking for it.

The group behind this presented at the Chaos communications congress in 2007 and demonstrated controlling a UAV over the internet the video is very interesting and can be found here

http://video.google.co.uk/videoplay?docid=6900719579308461104

or on your favourite peer to peer network etc as is creative commons licensed.

Launch vehicle / lifting craft

Don't forget the temperature

A lot of the suggestions involve batteries and latex. These may work at sea level but may have problems in the chillier climes of the upper atmosphere. Bearing in mind that testing the systems at the boundaries of space is quite difficult, the release mechanism must be unaffected by extremes of temperature.

What about using the expansion of water as it freezes. You could rig a blocked syringe as a piston assembly to unlock a gate. I guess the water could be 'doped' to operate at the required temperature.

@Jasmine

Uou mean turn *on* the current, right, Jasmine?

You could improve on that basic design by liberally coating the tether with black powder out of devil-bangers (or the contents of a firework), although this might pose some danger to a paper-based aircraft.

In the interests of helping the plane fly, it'd be a plan to put the separation mechanism on the balloon side of things. OK, you won't get it back, but that's not a major issue, whereas adding extra payload weight to your paper plane probably is. And it also solves other problems like wires and batteries getting hot.

As regards "assisted" paper, it's worth looking at how hang-gliders are built. Lolly-stick kingpost and kite-string luff lines to ensure it automatically recovers from a dive. Plus a decent amount of dihedral on the wings held in place by futher kite-string lines on the underside, so that it's stable side-to-side. Oh, and plastic-coated paper might also be a plan, to prevent condensation and general papery sogginess causing a Mission Fail.

@By Anonymous Coward Posted Monday 10th August 2009 11:34 GMT

separation

While I wasn't into free-flight model aircraft in my yoof, I recall that they had two methods used to trigger a modification in the aerodynamics leading to an enhanced rate of descent. One was a clockwork timer and the other was a burning fuse which passed through a rubber band. The rubber band broke when the burn reached it. The clockwork timer was more accurate, but selecting the length of the fuse appears to have provided adequate accuracy. I suspect that the fuse approach may have some difficulties in our project caused by the lack of oxygen and the cold, which might extinguish the fuse, or fail to break the rubber band, or the rubber band may be sufficiently frozen to retain its shape and hence fail to release our craft.

condom, toilet roll & gaffer tape

Insert a condom into used toilet roll. Inflate the condom, until it is nice and snug, then seal one end with gaffer tape.

As the air pressure decreases, the condom will inflate, and the tip will push out of the open end of the roll. Position a release switch an appropropriate distance away, and wait for the condom to achieve the appropriate erection...

Release mechanism

If a weather balloon is being used to launch the spacecraft, then it'll pop automatically when it reaches the highest altitude possible. A single-axis accelerometer (plus a microcontroller to do a bit of processing) will be able to provide an electronic signal indicating when the aircraft changes direction from 'going up' to 'going down'. There's a risk that the balloon pop could damage the spacecraft, so maybe the release should simply be triggered by a countdown timer from launch. Or a barometric sensor (e.g., http://www.sparkfun.com/commerce/product_info.php?products_id=8161) could trigger the release at a given height.

The release itself could be made from a piece of string tied around/alongside a low-ohm, low wattage resistor. Apply a modest current and the resistor will be set on fire and burn through the string, releasing the aircraft. Further experimentation will be required to see identify what weight of batteries could provide sufficient current. Failing that, I recall an article in the Anarchists Cookbook (or similar publication) about making an ignition device using a diode taped to a match-head. Once enough backward current is applied to the diode it heats up and set's the match alight. But of course both of these assume that there's enough oxygen at release height for a fire-based release mechanism.

Although not as exciting, a mini solenoid could be an alternative to un-hook the spacecraft from the balloon: e.g., http://www.rapidonline.com/searchresults.aspx?mode=b&kw=&manu=Dialight+BLP.

RE: Diminutive Crew?

I have done some of this before

Lithium ion and lithium polymer batteries are useless at low temperatures. There was a lot of laughter here when commentards found out that a mini-sub was powered by a crate full of D batteries. That only had to work down to 0 centigrade. I have not seen batteries quoted for really low temperatures, so you might be looking for some sort of thermos flask for the batteries.

Looks like you spotted the problem with GSM: at altitude, many cells will be within range. The network operators will not be happy if you broadcast to a dozen cells at once. I have not done APRS, but I suspect it has some of the same challenges for the power supply as GSM. The average power may be reasonable, but the radio needs to take sharp bursts of power. This means you will need short leads and good contacts between the radio and the battery. Some kind person replaced my gold plated folded sheet metal contacts with helical steel springs (inductors with a huge contact resistance). That was sufficient to prevent the GSM module getting the sudden bursts of power it needed.

For release, I would go test the following in a freezer: Connect the balloon to the decent module with fuse wire and break it with a large current. Go nuts on the current because the fuse wire will get covered in ice. Use multiple methods for deciding when to release: GPS reports target altitude, GPS reports minimum acceptable altitude and consistently descending, time limit and remote control from your radio (you never know - it might still be working).

Read the instructions for your GPS. Many of them are optimised on the assumption that you must be on the surface of the earth, and that you want the signals that have been reflected off buildings (Reflected signals cause multipath error, but that may be preferable on the ground when the direct signals are blocked). There are often manufacturer specific 'NMEA' commands that will reconfigure a GPS for use at altitude.

Passive antennas will work at very low temperatures - if your GPS can use a passive antenna. If you have to use an active antenna, check the specs to find out if it will work at low temperatures. Read the real instructions for the antenna. The salesman will tell you what he thinks you want to hear. There are good signals at altitude, and plenty of satellites will be in view, but the kit will be working below the tested temperature range while covered in ice. Many GPS antennas assume they are stuck to the top of a car, and need a ground plane (sheet of metal about 30cm in diameter) to work according to spec (this include plenty of antennas for hand-held GPS devices). Use a coating that repels water: you can get them in spray cans (Often very poisonous. Read the instructions carefully and do not use indoors). Spray all the electronics as well (except the connectors).

It is safe to assume your GPS and your radio will not work at the same time. If you cut the weight by removing the RF shielding from you GPS, radio or CPU then none of them will work at the same time. Make sure you can send the last __valid__ GPS fix. If the parts work individually, but not when packed together, add small capacitors connecting each connection between modules to ground. If you cannot keep the GPS and radio antennas apart, point the radio antenna's weakest transmission direction at the GPS antennas worst reception direction. The frequencies are very different, but putting a powerful radio transmitter right next to a very sensitive receiver is always asking for trouble. GPS likes short antenna cables - especially if you use a passive antenna. The really thin light weight cable is poorly shielded and will pick up too much signal from everything that can confuse the GPS.

PARIS should be a manned mission...

Balloon-popping systems

Might not work very well- you'd have to do a lot of testing to make sure it'd work. Balloons are very thin sheets of rubbery stuff, and at height they'll lose a load of their flexibility- you may even get to the point where it becomes rigid, then when it gets punctured you'll have to wait for it to thaw out before it bursts properly.

How about a couple of bits of memory metal? GPS calculates height, so when GPS recognises that you're at height it jams a few mA through the metal- heating it and causing it to bend straight again. So you'd have a venus-flytrap style arrangement on the carrier to hold the Vulture 1 in position.

Alternatively, how about a GPS-switched capacitor & piece of thin copper wire wrapped around a balloon full of mixed hydrogen & oxygen? The balloon could hold a trap door shut, so when the gas is ignited and the balloon bursts the Vulture 1 falls through the trap door.

Two non-techy tips

@Kieran

Right with you on that! Dog-simple! They're the ones that usually work! Minimal extra weight - should work, unless it ices up.

Camera? Seriously stripped down 'phone. Maybe get live piccies, and the battery could maybe power the GPS also? After all, it aint gonna last long...I still think 'splatdown' rather than 'splashdown' is quite possible, esp. when the thing gets wet, hence the papier maché suggestion.

Probably need something like a clothes peg* on the other side of the pin for the launch, to prevent premature ejac^H^Hection from PARIS at lift-off.

Nice one, AC 11:34. Gets my vote, too.

* OK, for the IT angle, a crocodile clip might be better. Then Maplin, Farnell or RS etc. could sponsor it! YaaaaY!